1. Field of the Invention
The present invention relates to a device for fusing a predetermined toner image on paper. More particularly, the present invention relates to a fusing device which controls the heating range of a fusing unit by inputting an eddy current generated by a transformer to a terminal corresponding to the size of paper selected from a plurality of terminals of the fusing unit.
2. Description of the Related Art
A conventional image printing apparatus comprises a fusing device which applies a predetermined pressure and amount of heat to a toner so as to fuse a predetermined toner image on paper. The fusing device includes a fusing unit which applies a predetermined amount of heat to the toner, and a pressurizer which applies predetermined pressure to the toner. The fusing unit includes a heater which generates heat used to fuse a toner image on the paper, and a toner fusing layer which transfers heat generated by the heating body onto the paper.
FIG. 1 is a schematic cross-sectional view taken along a lateral plane through a conventional fusing unit 10 of a fusing device using a halogen lamp as a heat source. Referring to FIG. 1, the fusing unit 10 comprises a fusing roller 11 and a heating body 12, which is comprised of a halogen lamp installed in the center of the fusing unit 10. A coating layer 11a made of Teflon is formed on the surface of the fusing roller 11. The heating body 12 generates heat, and the fusing roller 11 is heated by radiant heat transferred from the heating body 12.
The fusing unit 10 of FIG. 1 is used to apply heat to a sheet of paper. There are many types of papers, such as A4, A5, B5, and so forth, used in an image printing apparatus. Recently, many types of photo paper sizes, such as 3×4, 3×5, and 5×7 inches, have also been provided for directly printing photos using the image printing apparatus. However, a conventional image printing apparatus heats the entire surface of a fusing roller regardless of the size of paper to be printed. Thus, when a toner image is printed on paper having a smaller size than that of the fusing roller, there is a large temperature difference created between a region in which the paper passes through the fusing roller, and a region in which the paper does not pass through the fusing roller. When the image printing apparatus is used over a long period of time, the image printing apparatus may malfunction due to the rapid temperature increase in the region in which the paper does not pass through the fusing roller. In addition, due to uneven heating of the fusing roller, the life span of the image printing apparatus is reduced.
Additionally, in a conventional fusing unit using a halogen lamp as a heat source, a warm-up time of several seconds to several minutes is required for the unit to reach a target fusing temperature after energy is supplied to the fusing unit. Thus, a user is required to wait for a long warm-up time when printing an image, regardless of the paper size.
Accordingly, a need exists for a system and method for more efficiently and quickly heating a fusing unit by considering a paper size.